class_docstr: Represents a sub-structure of a OverlayGraph.
  
  Often, we want to find structures within a graph, such as branches and
  sequences, to assist with graph layout for users.
  
  An OverlayStructure represents such a structure. It is typically used
  in conjunction with OverlayGraph.collapse_structures() to parse a graph.
code: def __init__(self, structure_type, structure):
      self.structure_type = structure_type
      self.structure = structure  # A dictionary
      self.children = sum(
          [
              component
              if isinstance(component, (list, tuple))
              else [component]
              for component in structure.values()
          ],
          [],
      )
  
imports: from collections import defaultdict
  import numpy
  import tensorflow
label_desc: Use image node_id 1 to create a new OverlayStructure object  with example: obj = OverlayStructure(structure_type, structure)